EP2828164B1 - Device for detecting critical states of a surface - Google Patents

Description

Technical area

The detection of ice formation on surfaces (including surfaces) such as on the rotor blades of wind turbines can contribute significantly to maintaining safe operating conditions. In the field of wind turbines, an ice coating causes lower energy yield and higher mechanical stress on the system and at the same time poses a risk of ice shedding (a hazard for both humans and goods). Already thin layers cause due to the turbulent flow at the surface due to greater roughness relevant yield losses. Thicker layers can lead to damage to the machine as a result of increased vibrations and imbalance and to damage when dropped. As the operator of wind turbines at endangered locations, it is now interesting to know the degree of icing of the rotor blades as well as possible in order to shut down the wind turbine in good time before damages occur or to selectively activate any existing electrical heating of the rotor blades.

However, ice formation is also a relevant phenomenon in other areas such as on roads, aircraft wings or antennas, the early detection and elimination of which by appropriate measures facilitates trouble-free operation.

State of the art

Current commercial systems for the detection of icing are typically complex measuring devices and fixed in the vicinity of wind turbines due to their size and typically require a power connection due to their structure (eg optical and ultrasound-based systems). It is known in the art that the Aneisungsverhalten eg in wind turbines at the location of the nacelle and on the rotor blades can significantly differ (eg, by the resulting higher speed from the rotation of the wind). Therefore, systems were further developed that investigate the Aneisungsverhalten the rotor blades, eg by monitoring the condition of the rotor blade by means of natural frequency analysis. This system has the disadvantage that not only ice coating can lead to the change of the natural frequencies. Furthermore, the detection threshold is relatively high (about 4% weight change) and no localization of the ice layer is possible. Furthermore, a system is known which uses an optical ice detection principle by guiding optical fibers from the inside to the surface of the rotor blade ( DE 102005017716 A1 ). This requires the installation of a complex measuring device in the rotor blade and thus high installation costs, further injury to the surface and it allows the measurement only at a few points per rotor blade.

Methods for the detection of moisture or humidity by absorption to a porous carrier and evaluation of a complex impedance are described, for example, in US Pat FR 2750494 A1 and US5177662 described. However, these methods are in principle not able to detect the presence of ice or a layer thickness, since the absorption-based method requires that moisture can penetrate into the interior of the sensor.

In contrast, methods for ice detection are known, based on the measurement of electrical capacitance or impedance (eg US 5398547 ). These methods are particularly suitable for a planar construction with low height.

DE 10205017716 uses the wireless transmission of signals over a transmission link to a receiver as a measuring principle for detecting deposits as obstacles in an optical transmission path as a method of ice detection on the surface of a rotor blade. WO 2009/052828 is considered to be the closest prior art.

Object of the invention

The object is as follows: a device for detecting critical surface conditions, wherein the most vulnerable surfaces are typically not planar (e.g., in aircraft, rotor blades, high voltage insulators, or antennas). The surface shape or its nature must not or not significantly changed by the sensor, for example, to change the behavior with respect to a Anise or not minimal. The aerodynamics may not be influenced by the device or only slightly. As ice in the context of the invention, all types of frozen water are to be understood as mixed with liquid water. If necessary, classification of the type of ice or detection of situations in which there is certainly no ice on the surface may be of interest. For the purposes of the invention, water also includes mixtures of water and impurities of the surface.

Critical surface states in the sense of the invention are in particular the following scenarios: water and / or ice and / or mixtures thereof on surfaces (eg rotor blades) of wind turbines, ice and / or water and / or impurities on high-voltage insulators. there It is an object of the invention to detect emerging critical states so that countermeasures can be taken in a time window in which these critical states are still manageable.

The subject invention solves the problem, inter alia, that the device, which includes a device for detecting ice and / or water, for power supply and data transmission, at least partially designed to be mechanically flexible, so that an adaptation to non-planar surfaces is possible. The device may be hermetically sealed, i. no water or humidity can penetrate into the interior of the sensor; in particular, the interface with the environment is by no means porous. The integration into a unit and the geometric shape (among other things by the low height in relation to the length and width) are a first but also a subsequent attachment of the device to a surface to be detected in a simple manner and without major changes to the Surface possible. The acquired and evaluated data can be transmitted wirelessly or by wire to another device or to a base station, which need not necessarily be located in the rotor blade and form no mechanical unit with transmitter and receiver.

Further details on embodiments and advantages of the subject invention are set forth below.

The attachment to non-planar surfaces requires a flexible design, especially large-scale components, in particular an at least partially flexible support plate, for example, from two flexible circuit boards, which can simultaneously represent the outer skin, running with intermediate filler (for example, Polymerverguss) is, whereby a mechanical connection of all components is guaranteed.

Furthermore, a low strength of the individual components and small dimensions of rigid components are required. The total thickness is in the low single-digit millimeter range; Thicknesses of less than 5 mm are advantageous and allow a ratio between the greater side length and the thickness of the device greater than 10.

The sensor for ice detection and / or ice thickness measurement and / or ice classification can be designed for example as a capacitive sensor. A capacitive sensor for ice detection and / or ice thickness measurement consists of a plurality of electrodes of conductive structures, which may be applied, for example, on a flexible, non-porous, ideally hermetically sealed carrier material (ie low water absorption / low water permeability of the carrier material), and an evaluation unit Measures capacitances between largely planar arranged electrodes and returns from it a value for detection and / or thickness. The material of the interface between the sensor and the outside world should also be largely hermetically sealed, which means that the material has almost no permeability or absorption capacity for water or water vapor.

Other sensors included in the device can measure, for example, brightness, oscillations, temperature and / or electrical currents. In particular, leakage currents (direct and alternating currents) along insulating surfaces, such as high-voltage insulators, on which the device can be mounted, are of interest.

The assembly of the device can be achieved by adhesion to a surface to be observed (with or without application of further protective layers over the device) or by embedding eg in outer layers of a rotor blade during the manufacturing process. As a result, no mechanical intervention (drilled holes, slots, recesses) in the surface to be observed is necessary.

For example, self-adhesive films (above or below the device), spray adhesives, liquid adhesives may be used in the bonding. In a preferred embodiment, an adhesive is already applied to the device in the manufacturing process and covered with a protective film until it is assembled, so that only the protective film must be removed during assembly and the device can be attached directly to the surface to be observed.

A typical surface treatment (if electrically or only slightly conductive) can also be applied above the device so that the original surface finish remains guaranteed.

The electrical energy required for operation can be obtained from the environment: these are, for example, flexible solar cells based on GaAs or amorphous silicon. Furthermore, an energy recovery from heat (thermoelectric generator) or from vibrations of the surface can be used. These are also technologies that can be realized with low height and / or largely flexible.

The electrical energy necessary for operation is temporarily stored in an energy store. These typically rechargeable energy storage can also be implemented in a flexible design. This can be, for example, accumulators or capacitors (also Supercaps etc.). Furthermore, a (flexible) primary cell (battery) can be used.

The data transmission of the acquired measurement data may advantageously be wireless (i.e., for example, over optical links or over the air) in order to make connections for data transmission obsolete, in addition to a connection to the power supply; thus no cabling is necessary. In this case, the device can be completely hermetically sealed, i. no substance (e.g., water or humidity) can penetrate the interior of the device. This increases the robustness of the system.

Several such devices can optionally communicate with each other, on the one hand to limit the distance to be bridged by the data transmission by radio (and thus the energy consumption), and on the other hand to increase the reliability and the statistical quality of the measured data.

One possible application of such devices is ice detection and / or ice thickness measurement on the surface of rotor blades of wind turbines. Here, the device can also be used to control devices for defrosting the surfaces of rotor blades (eg hot air blower, surface heater). The low weight, the low height and the longevity of the device are of particular use here. In this case, the device can be integrated, for example, in a surface heating and applied together, whereby the device with the device for defrosting can form a mechanical unit. Here it is possible to use the heat flow from the heating in the environment for thermoelectric energy production. Furthermore, there is the possibility of conductive parts of the heater as electrodes for ice detection or ice thickness measurement (capacitive ice sensors), whereby the device can also electrically form a unit with the device for defrosting. In certain circumstances, the device may also be attached to the inside of the rotor blade.

The invention relates to a device for detecting and measuring thickness of ice and water on surfaces and is characterized in that the assemblies for energy production from the environment, energy storage, data processing and wireless data transmission are already included in the device, the entire device is thin and is flexible. Thus, the device can be without major mechanical intervention in the equipment to be equipped with the device, even later, attach. The individual devices can optionally not only communicate with one base station but also with each other, but work independently of each other.

The present invention is as follows: a device for the detection of critical surface conditions (eg quantification of ice and water on surfaces), wherein all components for power supply and data processing and data transmission are included in the device and the entire device thin (height less than 5 mm or ratio between the greater side length and the thickness> 10) and at least partially flexible (flexible) is executed. Due to the low height, changes in the aerodynamics are minimized and thus also changes in the Aneisungsverhalten avoided by the device.

Enumeration of the drawings

• Fig. 1 ein beispielhaftes Blockschaltbild der Vorrichtung darstellt,
• Fig. 2 eine beispielhafte Ausführungsform der Vorrichtung im Profil zeigt,
• Fig. 3 eine Draufsicht auf eine beispielhafte Ausführungsform der Vorrichtung zeigt und
• Fig. 4 beispielhaft ein Rotorblatt mit möglichen Montageorten für die Vorrichtung zeigt.
• Fig. 5 beispielhaft die Montage der Vorrichtung auf einem elektrischen Isolator zeigt.

The invention will be explained in more detail with reference to an embodiment according to the drawings, wherein

• Fig. 1 an exemplary block diagram of the device represents
• Fig. 2 shows an exemplary embodiment of the device in profile,
• Fig. 3 a plan view of an exemplary embodiment of the device shows and
• Fig. 4 exemplarily shows a rotor blade with possible mounting locations for the device.
• Fig. 5 shows by way of example the mounting of the device on an electrical insulator.

Detailed description using the reference numerals in the drawing

As in Fig. 1 In addition to a sensor for ice detection and / or ice thickness measurement and / or ice classification 4, the device 100 includes a system for generating energy from the environment 1 (eg from solar radiation, heat, vibrations or leakage currents, electric / magnetic / electromagnetic field). These energy sources are typically not continuously available, which is why the energy can be temporarily stored in an energy store 3. Both modules are optionally flexible and thin. The regulation is carried out by an energy management system 2.

A control unit 5 (for example, a microprocessor) is supplied with energy from energy store 3 or the system for generating energy from environment 1 and acquires measurement data from the sensor for ice detection and / or ice thickness measurement and / or ice classification 4. These data can be combined with further measurement data from further Sensors 6 (eg temperature, electricity) are processed and are over a device for data transmission 7, for example, wirelessly via a radio link 8 to another device 100 'or a base station 9 forwarded. Depending on the location and environmental conditions, different devices for energy generation and storage (also several systems in a device 100) can be provided.

FIGS. 2 and 3 show the exemplary schematic structure of the device: a rigid or flexible solar cell 10 is located at or below a surface to be observed and is separated from the environment by an at least partially transparent protective layer. A flexible battery 11 is located within the device 100 which is surrounded by an outer skin 12 (eg, a flexible circuit board). The entire interior is filled with a (possibly reinforced) filler 14 (eg a polymer). The outer skin 12, which may for example be designed as a flexible printed circuit board, forms with the filler 14 is a mechanical unit with the function of the flexible support plate 21. Also within the device 100 are other devices such as electronic components and integrated components 13 for data processing, measurement and data transmission , The electrodes for ice detection or ice thickness measurement 15 are located below the surface of the device 100 to be observed. The radio antenna 16 is also integrated in the device 100 and may also be below the surface 0 to be observed.

Due to the described features, the device 100 may be hermetically sealed (completely electrically isolated), whereby a particularly long unrestricted operating time can be realized. Furthermore, the entire device 100 is thin (height below 5 mm or ratio between the largest side length and thickness greater than 10) and flexible (flexible) executed. The flexible version large-area, thin components with simultaneous use of a flexible substrate, the arrangement of the components to each other and small dimensions of rigid components contribute significantly to the flexibility of the device 100 at.

Fig. 4 shows three of many possible mounting positions of the device 100 on a rotor blade 20 of a wind turbine: Device 100 and device 100 'at the leading edge of the rotor blade 20 are positioned significantly more relevant than device 100 ", as experience shows starting at the leading edge and depending on the manufacturer only this area is equipped with a defrosting device 22. Typically, the curvature of the surface O of the rotor blade 20 is particularly pronounced precisely at these positions, which makes an at least partially flexible device 100 necessary for the measurement Therefore, it is necessary to have a fastening method with the least possible height requirement (gluing or integration by lamination) and a low overall height of the device 100. Protective layers over the device 100 are unproblematic if not conductive and possibly transparent sch. In addition, by using similar materials and comparable height, the device 100 can be integrated, for example, in a surface heating such that a common assembly or the sharing of conductive structures is possible.

The acquired measurement data are, for example, transmitted by radio in a sensor network to another device 100 'or device 100 "for further transmission or are transmitted directly to a base station 9 for evaluation and / or control of a device for defrosting 22. In this case, the design as a sensor network be beneficial to those of the Radio transmission to bridge the distance (and thus the energy consumption) to reduce; On the other hand, several measurement points are useful to ensure the redundancy of the system and to ensure the high quality of the recorded values.

Fig. 5 shows one of many possible mounting positions of the device 100: Attachment of the device 100 "'to the surface O of an insulator 23 of high voltage transmission equipment (eg overhead tower, transformer bushing) allows, in a suitable embodiment (eg annular, mounting to mounting position 24), the measurement of unwanted leakage currents along such surfaces by means of contacting or non-contact methods of current measurement (eg Rogowski coil, fluxgate sensor, shunt resistor).

Claims (8)

1. A device (100, 100"') for detecting critical states on a surface of a component part (20), characterised by
   an at least partially flexible carrier plate (21), which can be fastened to the surface (O) and which is mechanically integrated into a unit together with at least one sensor (4) for detecting critical states of the surface, an electrical energy store (3, 11), a device for electrical energy harvesting, a control unit (4) for detecting and processing the sensor data and also a data transfer unit for wireless data transfer, wherein at least the sensor (4) is hermetically sealed.
2. The device (100,100"') according to Claim 1, characterised in that the device for electrical energy harvesting comprises a solar cell (10).
3. The device (100, 100'") according to Claim 1 or 2, characterised in that it is thinner than 5 mm.
4. The device (100, 100"') according to one of Claims 1 to 3, characterised in that it can be adhered to the surface (O).
5. The device (100, 100'") according to one of Claims 1 to 4, characterised in it is integrated beneath the surface (O) into the component part (20).
6. The device (100, 100"') according to one of Claims 1 to 5, characterised in that the sensor (4) is a capacitive sensor for detecting icing with a number of electrodes (15) made of conductive structures.
7. The device (100, 100"') according to one of Claims 1 to 6, characterised in that the sensor (4) can be fastened to the surface (O) of a component part (20), which has a device (22) for defrosting the surface, wherein the device is used to control the defrosting device (22).
8. The device (100"') according to one of Claims 1 to 4, characterised in that the sensor is configured to measure leakage currents at the surface (O) of an insulator (23).

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